Pressure sores, also called decubitus ulcers, are injuries to the skin and underlying tissues caused by direct pressure over time to superficial tissues, including weight bearing over bony prominence, and shearing force on the skin. They can be exacerbated by excessive moisture on the skin, occlusion of lymphatic vessels, stress and smoking.
Pressure sores range from a very mild pink coloration of the skin, which disappears in a few hours, to a very deep wound extending through bone or into internal organs. These sores are classified in stages according to the severity of the wound. The most common scale to assess pressure sores is the National Pressure Ulcer Advisory Panel Scale which grades sores by 4 grades. Stage I is a non-blanchable erythema of intact skin. Stage II is partial loss of skin thickness where the ulcer presents as a skin abrasion. Stage III involves full loss of skin and necrosis to underlying fascia. Stage IV involves skin and fascia and or bone and muscle necrosis.
Pressure sores are a common medical problem causing substantial morbidity. For example, the incidence of pressure sores during hospitalization from stroke is 21%. The incidence of pressure sores is over 30% per year in patients with spinal cord injuries, and after hospitalization from stroke. The incidence of pressure sores is 41% in elderly patients discharged from a nursing home without stroke. Even pregnant women in hospitals are susceptible to pressure sores.
Once pressure sores develop, they can take months to heal, or can remain chronically open sores. They often become infected leading to local abscess and septicemia.
Treatment of pressure sores include removal of the cause, the application of topical substances, debridement, and surgical procedures where the wounds are covered with tissue flaps. However, these treatments are often unsuccessful and, even when successful, are associated with a high recurrence rate.
Other types of soft tissue wounds may include, but not be limited to, diabetic ulcers, burns, and surgical incisions. Diabetic ulcers cause over 70,000 amputations a year in the United States alone. A method and system for treating such pressure sores and other soft tissue wounds would be desirable.
It is known to use electrical stimulation to promote healing of soft tissue wounds. Previous studies of electrical stimulation to treat pressure sores employed electrical stimulation with variation of stimulation parameters, such as current and waveform. Almost all modes of stimulation healed sores to some extent, but no studies optimized stimulation parameters. Additionally, the electrode placement and cross sectional area of the electrodes varied, the extent of the sores (stages I–IV) varied, as did the length of time the areas were stimulated.
For example, with reference to FIG. 1, one prior art system uses two electrodes 10 disposed closely adjacent to and on opposite sides of a wound 12 so that the path of current is across the wound. Modified square wave DC biphasic pulses are used, up to 100 pulses per second. Since the electrodes are placed across the wound, however, the electrical stimulation travels in a path of lowest resistance and the pattern of current flows between the two electrodes resemble that of Maxwell field lines as shown in FIG. 1, with the highest intensity through the center and intensity reduced exponentially, the further away the tissue is from the shortest line connecting the two electrodes. Therefore, for wounds that are irregularly shaped, or wounds that are deep such as stage 4 pressure sores, very little current actually travels into the wound, and electrical stimulation of such pressure sores results in low rates of healing.
For these reasons among others, while therapists use electrical stimulation to treat pressure sores, there is no FDA approval of electrical stimulation for treatment of pressure sores or other soft tissue wounds. Further, conventional systems are expensive and complex. Therefore, it would be useful to have a system for the application of electrical stimulation to pressure sores that optimizes stimulation parameters. Further, it would be useful to have a system that a patient could use at home to apply electrical stimulation to a pressure sore.